LM3886/Vox SS Amp Thread(w/ Samples!)

[Joecool85]

It's cool.  I just wanna see.  It sounds to me like you got some nice stuff over there 

[RDV]

Here we go. 12 hour work day, another one tomorrow, vodka for supper, crappy camera, everybody yelling at me. Wife crazy.
Enjoy Pictures.

Thomas/VoxDean Markeley & Stereo Amp & Mackie recovered from Dumpster.



Insides of TV/Vox/Chipamp showing poweramp.


Inside of stereo amp.



Blurry pic.



...and another.


RDV

[RDV]

The controls on the guitar amp aren't what they seem. They are, left to right: Input,  Bass, Treble, MRB cap selector, MRB on/off, Volume, Limiter, Line Out.

RDV

[Joecool85]

WOW the heat sinks on that stereo guy are HUGE!

Also, since it seems you used one of the kits from chipamp (which I knew about) did you just use the schematic/resistor/cap values for their kit, or adjust it to be a guitar amp?

[RDV]

WOW the heat sinks on that stereo guy are HUGE!

Also, since it seems you used one of the kits from chipamp (which I knew about) did you just use the schematic/resistor/cap values for their kit, or adjust it to be a guitar amp?

I just used his values, there's not a lot of difference really. As far as I know the one at GGG is just from the app notes of the LM3886 datasheet.

I probably could've just used one of the heatsinks for that amp but I wanted to be able to push it hard if need be. Right now it's just hooked to the Mackie mixer with my computer running into it with 2 of those little metal speakers that Radio Shack used to sell with 4" woofers.

That stereo one will get really loud with good speakers!

Is that the same Dean Markely as your practice amp?

RDV

[Joecool85]

Nope, here is mine:



Behind it is the gutted Fender, and the rest of the stuff thats next to my bed 

[Joecool85]

If I was to buy the stereo lm3886 set from chipamp.com, along with a transformer, some pots and jacks, could I build an amp that would have one input jack for the guitar, and drive two separate cabs with 50w a piece?  If so...I may do that, its so much cheaper than doing a GGG board, chipamp.com power supply PCB, buying all necessary components etc.  Well, not a lot cheaper, but some, and instead of having a 1x50 amp, I could (in theory) have a 2x50 amp.  And I was worried about using their values etc for guitar use, but if it worked for you...I'm sure it'd work for me.  Then I'd just have to build a decent preamp/eq setup and bing bang boom, I got me 100w worth of guitar amp 

Then I can finally run what I really want to do.  (both custom built cabs, built by me) - a 4 x 8 cab and a 1 x 12 cab.  I think it'd sound sweet, and be pretty portable.

[RDV]

You could certainly do that by just paralleling the inputs.

That chipamp guys got a special for about 30 bucks where you get a stereo LM3875 amp kit. It would be plenty of power, and cheap.

RDV

[Joecool85]

WOW!  56watts @ 8ohms!  And a stereo one, so 2 x 56w for $35!  Sounds good to me.  Is there any downfall to using a lm3875 setup instead of lm3886?  Also, would it take the same transformer and stuff?  You the man RDV!

[Joecool85]

Also, it mentions that the lm3875 comes with rectifier boards...but the lm3886 kit comes with power supply boards...does this matter?

**edit**
In doing a little research, it seems that this is better in some ways for me.  I only care about 8ohm operation really, and it does that @ 56w.  The lm3886 only does 50w @ 8ohms, but is capable of 68w at 4ohms (although really, really hot).

[RDV]

The rectifier board on that also has a place on the bottom of the board to place big filter caps like the ones I used on my stereo version. I looked at the caps I used(see link) and Mouser's out of them but they will fit perfect on the bottom of that(LM3875) rectifier board and they were cheap.

Is that Dean Markley a keyboard amp? Mine is ancient(like me)! I bought it in 1985.

RDV

[Joecool85]

I'm confused...where do the 10000uF caps go?  it lists using 1000uF caps or something if I remember right.

And my dean markley is a K-20X.  It is a guitar amp and has a built in overdrive channel that you can only switch by the button on the front.  8" speaker, 15w amp.  It's alright for practice etc.  Not insanely loud, but enough to bug the neighbors if its up all the way.  As far as age goes, its not very old, I bought it new in 2002.

[RDV]

I'm confused...where do the 10000uF caps go?  it lists using 1000uF caps or something if I remember right.

Look Here & Here.

RDV

[Joecool85]

Ah ha!  I see.  Now, did you use the lm3886 kit, or the lm3875 kit? 

Does it really make a difference? 

What is the difference between a power supply PCB and a rectifier PCB?

And is it just me, or does the kit come with everything you need, except for the 10,000uF caps?

And lastly, would these work alright?
http://jameco.com/webapp/wcs/stores/servlet/ProductDisplay?langId=-1&storeId=10001&catalogId=10001&productId=157737&pa=157737PS

[Joecool85]

I might just do the stereo lm3886 kit anyway because its only $25 cheaper to do the lm3875 and I'd need to get the caps at roughly $5 a piece, so then its only $15 cheaper, plus shipping for the caps, so lets assume its around $10 cheaper...I dunno.  I don't see that either one has any advantage (lm3886 vs lm3875) except for a negligable wattage output.  I think I'd rather have everything I need right there in the kit.  Something to think about anyway.

[Joecool85]

Bump.  Any help RDV?

[RDV]

I haven't been able to log in for a while.

I think you'll be satisfied either way you go.
The instructions for the LM3886 kits are more detailed for sure, and all the parts are there.
I believe that you can build the LM3875 kit as it is without the 10k µF caps and be fine.
It's hard to say since I haven't built that one.
What I do know is that one was the 1st one he put out so I'm sure it works just fine without the added stuff.
In the end it's up to you.

RDV

[Joecool85]

What about dual mono?  What exactly does it do?  Like does a dual mono lm3886 put out 100w or is it still 2 x 50w?  If so, whats the point?  Why not use a stereo version?  And also, does that mean you did the lm3886 kit?

[RDV]

What about dual mono?

True dual mono would mean two completely separate circuits. Two transformers, two PS boards, two poweramps.

What exactly does it do?

Offer the extra headroom of two separate circuits, plus less stress on PS.*

Like does a dual mono lm3886 put out 100w or is it still 2 x 50w?

Well, 50 + 50 does = 100

If so, whats the point?

See*.

Why not use a stereo version?

I did.

And also, does that mean you did the lm3886 kit?

Yes, the Dual Mono one, but I built it as a stereo version so I could have the other PS board for another project.

RDV

[RDV]

If you'd like a mono 100 watt chipamp, you want to build the LM4780 kit.

Gee, I hope these guys send me some free stuff(at least some PCBs) for the references here.

RDV